Electric regulator



Dec. 4, 1928.

F. A. BYLES ELECTRIC REGULATOR Filed June 17, 1926 Fig. i.

Fig. 2.

VOLTS AMPERES lnvencpr 1 Frank A. Byles,

His Attorneg.

Patented Dec. 4, 1928.

UNITED STATES PATENT owl- FRANK A. BYLES, 0F SCHENEC'TADY, NEW YORK,ASSIGNOR T0 GENERAL ELECTRIC COMPANY, CORPORATION OF NEW YORK.

"nmc'rmc REGULATOR.

Application filed June 17', 1926. Serial No. 116,762. I

My invention relates to electric regulators and more particularly tocurrent regulators of the vibratory type for use in electrical 'sys--tems in which a constant current is desired.

The invention finds particular application in the motion pictureindustry where are lamps, and especially. direct current are lamps, areused as the source of screen illumination. As is well known, it isparticularly desirable to maintain constant current in the arc lampcircuit, since a small chan e in current causes a material change in t'e illumination on the screen. Many motion picture houses find .itdesirable to provide two projection machines so arranged that the secondmachine may be operated simultaneously with a machine'in operation for ashort period of time in order to change from one reel of film to anotherwithout delay. .This ms'ce'ssitates operating two are lamps either inparallel or in 'series. Arrangements in which thetwo lamps are; operatedin par allel during the change-over have. the disadvantage ofoverloading thege'nerator, if a motor generator set is used, and thenewly' started arc has a tendency to draw an unequal share of currentduring the initial periodof adjustment. Hence, it has been founddesirable to operate the arc lamps in series during the change-over.

If two projector arc ated simultaneously in series, the source of supplymust be capable of furnishing a constant current over a wide range ofvoltage in order to operate successfully a-single arc or a plurality ofseries connected arcs. The well known series are generator, designedwith a drooping voltage-current characteristic, approximates some of thecharacteristics desired, but does'not in itself secure constancy ofcurrent, in the arc lamp. circuit. Even if this drooping characteristicis exaggerated and the usual type of current regulator is used, theresult .obtained is only an approximately constant current. The resultsheretofore obtained may be sufiiciently accurate for generalillumination purposes butwhere a more rigorous current regulation isdemanded, as in motion picture projectors, an absolute constancy ofillumination is desired. It has been foundthat the known regulators arenot sufliciently sensitive or rapid in operation to accomplish entirelysatisfactor results. 4 1

- t, therefore, isan object of my invention lamps are-to be opertoprovide an improved current regulator capable of operating with agenerator having a. wide voltage range, which is. sensitive andsulficiently rapid in operation to maintain a substantially constantcurrentin a series are circuit during any operating condition imposedwhen arcs are used alternately or when a single or a plurality of arcsare operated continuously;

.The' novel featureswhich I believe to be characteristieofmy inventionare set forth with particularity in the appended claims.

The invention itself,however, both as to organization and method ofoperation, together with further objects and advantages thereof,

will be better understood by-reference to the following descriptiontaken in connection with the accompanying drawing in which Fig. Us adiagrammatic illustration of a system in which my invention has beenembodied, and Fig. 2 is an explanatory diagram showing a suitablevoltage current characteristic for the supply-generator.

In Fig. 1 a dynamo-electric machine 1 is shown diagrammatically as adirect currentgenerator. and may be driven in any conven-' ient manner,as, for example, by an alternating current motor (not shown) connectedto commercial supply mains. This dy-.

thereof is. controlled by the current regulator to be describedpresently. Arc lamps 5 and 6 provided with suitable electrodes, areshown diagrammatically in a. series circuit with the generator 1 and areprovided respectively with shortcircuiting switches 7 and 8, whichprovide a means for putting any desired lamp' or lamps into operation.

As shown in the. drawing, a regulator 9 is arranged to control the shuntfield excitation of generator 1 so as to maintain the current constantin the arc lamp circuit. Regulator 9 comprises cooperating-contacts 10and 11, a-core 112, and windings 13,14. and 15.

The contact 11 is arranged to be stationary and is screw-threaded toprovide a means for adjusting the contact gap so that the regulator maybe arranged to hold difi'erent current values. The contact 10 isarranged to be movable and is resiliently mounted in order to permit ahigher contact speed than is possible with a moving contact mechanismhaving appreciable iinertia. Contact 10, as shown, is supported by meansof a spring 16 formed of a light, thin, fiat ribbon of steel, rigidlyattached at its ends to a fixed support 17 which-is secured to the core12. Adjacent the contact 10, and approximately at the middle of thesupporting spring 16, is secured a magnetic armature 18, which isarranged to cooperate with the core 12 and its operating windings 13, 14and 15. Winding 13 is connected in series relation with the load circuitandis of low resistance and commonly constructed of a few turns ofrelatively large wire. lVith normal changes in current, the action ofwinding 18 would be entirely too sluggish to efiect the rapid correctiondesired. To provide a rapid vibratory movement of contact 10, winding 14is connected in series with a resistor 19 across the shunt field winding2 and is arranged to act accumulatively with winding13. The action ofthis winding, however, has a tendency to cause the regulator to hold alower current, as the operating voltage of the generator increases. To

compensate for this tendency, I provide a winding arranged to actdifferentially with respect to windings 13 and let. Windlng 15 isarranged to be responsive to the voltage impressed upon the load circuitand is connected in series with a resistor 20 across the terminals ofgenerator 1.

The cooperating contacts 10 and 11 are arranged to actuate'a relay 21,which is provided to periodically shortcircuit or insert the resistance4; in the circuit of field winding 2. Relay 21 comprises an operatingcoil 22 and contacts 23 which are connected in a parallel circuit toresistance 1. A condenser 21 is connected across contacts 23 in order toprevent excessive sparking. 22 is'arranged to be responsive to thevoltage impressed upon the load circuit and is connected in series witha resistor 25 across the terminals of generator 1. The main controlcontacts 10 and 11 of regulator 9 are so connected as to shortcircuitthe relay n'iagnet winding 22 when they close. This sequence ofoperation means that the relay contacts and main control contacts willopen and close together when in operation.

- Similarly to the conditions existent with the usual type of vibratoryregulator, the resistance a is of such a magnitude that it hasconsiderable eilect on the voltage of generator 1 and, when included ina circuit with the shunt field winding 2, reduces the voltage of thegenerator considerably below the de- The operating coil sired value and,when removed therefrom, allows said voltage to increase considerablyabove the desired value. It, therefore, the contacts 10 and 11 berapidlyopened and closed, the contacts 23 will be opened and closedandthevoltage of the generator will be repeatedly varied and itsvalueavill depend upon the relative length of the periods during whichthe contacts are opened and closed. The length of these periods willdepend upon the distance by which the fixed and moving contacts areseparated at each vibration, and this distance will be determined by theattracting flux in the core 12..

Let it be assumed that the dynamo-electric machine is in operation withthe electrodes of the respective arc lamps ant separated. For purposesof explanation, let it beassumed that the dynamo-electricmachine 1 isdesigned to have an open circuit voltage of say, 180 volts, which dropsto approximatelyvolts, when one lam) is burning and automaticallyincreases its voltage to approximately 120 volts, when the second are isstruck. fissulne, now, thatshortcircuiting switch 8 is closed and thatare lamp 5 has been put into operation and is burning with an impressedvoltage of aproximately volts and a current of approximatelyamperes'flowing in the circuit. This point of operation may, forconvenience, be considered to be atp'oint A on the voltage-amperecharacteristic shown in Fig. 2. Now assume that the arc conditionschange and that regulator 9has'bcen adj usted to hold 80 amperes.

If contacts 10 and 11 are in the position shown, contacts 23 will beopen and the Yul.

age impressed upon the field winding 2 will be a minimum. The winding 14of the regulator 9 will, at this instant, have a minimum energization,and, hence, the spring 16 will move contacts 10 and 11 into engagement.Upon the engagement of contacts 10 and 11, the winding 22 of relay 21 isshortcircuited so that contacts 23 will be closed to shortcircuit theresistance-4, and the voltage impressed upon the field winding 2 willthere upon increase to a maximum. Upon an increase in the voltage acrossthe shunt field winding 2, the energization ofwinding 14 will increase,whereupon the contacts 10 and 11 will be disengaged. Contacts 28 willagain be opened so that the voltage impressed upon field winding 2 isreduced to a minimum. This cycle of operation is rapidly repeated andthe contact 10 is rapidly vibrated by the operating winding 14. If thecurrent in the load circuit varies, the energization of the currentwinding 13 will be changed to vary the mean position of the vibratingcontact 10 so that the voltage of generator 1 will be varied to maintainsubstantially constant current in' the load circuit.

If the load circuit resistance increases, it will be necessary toincrease the generator voltage in order to maintain the currentconstant; This means that contacts. and 11 must remain. in engagementmore of the time.

However, with an increase in voltage, the

voltage impressed across the operating winding 14 will tend to maintaincontacts 10 and 11 out of engagement for a longer period of time, andthis would tend to 'cause a lower voltage to be generated, and hence alower current to be held than would correspondingly be held at lowervoltages. In order to compensate for thiseflect, windin 15 is ar--ranged to operate difierentially with respect to winding 14. Sincewinding 15 is energized in response to the terminal voltage of generator1, it will tend to maintain contacts 10 and 11 in engagement for alonger period of time .as the voltage increases, and hence will coun-'teract the tendency of winding 14 to regulate for. a lower current asthe voltage increases. Now, if it is desirable to start the second lamp6, its electrodes are brought together and the. shortcircuiting switch 8is opened.

This permits the current through the first lamp to flow through the tipsof the electrodes of the second lamp. The are is then struck andthe twolamps are now operating inseries and may, for convenience ofexplanation, be considered as operating at thepomt .B -onthevoltage-ampere characteristic shown in Fig. 2. The operation of theregulator under these conditions will be evident from the descriptionpreviously given in con- .nection with the operation of one lam sincethe current in the load circult 1s stil maintained at the same value andcoils 14 and 15 are subjectedto an increase in voltage of thesameproportion.

1 If it is now desired to change over from one lampto the other, theelectrodes of the first lamp are brought together and theshortcircuiting switch closed so that the (projec- 'tion may becontinued with the secon lamp.

While I have shown and described a particular embodiment of my inventionand a particularly, useful application thereof, it

will'be apparent to those skilled in the art that the invention may beapplied in other relations of utility and changes and modifications maybe made without departing from my invention, and I, therefore, aim inthe appended claims to cover all such changes and modifications as fallwithin the true splrit and scope of my invention.

' What I claim as new and desireto secure by Letters Patent of theUnited States, is,-

1. In combination with a enerator having ed to operate with a droopingvoltage-current characteristic, of a regulator. for maintaining constantcurrent in said load circuit comprising a wlndmg responsive to thecurrent in said load circuit, a .winding responsive to.

the voltage of said field-1 winding and arranged to operate-accumulatively with respectto said current winding, a vibratingcontact. comprising a resiliently supported contact member actuated bysaid windings,.

and a winding responsive to the voltage of said generator and arrangedto operatedif ated by said windings, and a winding responsivetotheiwoltage of said generator for Inodifying the action of saidvibrating contact throughout the voltage range of said generator.

In witness whereof, I have hereunto set my hand this 16th day of June,1926.

. FRANK A. BYLES.

a field winding and a load c1rcuit and adapt-

